The subject of the present invention is a suspension device for tire carcasses; more precisely, the invention relates to a suspension device for holding uncured carcasses during manufacture of the tires, keeping their axes substantially vertical. Hereinafter, this type of suspension will be designated by the expression xe2x80x9cvertical suspensionxe2x80x9d. The invention also relates to a process for building a tire using said device.
It is known that current manufacture of radial-carcass tires can be carried out in several stages: first of all, on what is called a xe2x80x9cfirst-stagexe2x80x9d machine, or alternatively a xe2x80x9cbuildingxe2x80x9d machine, on which the carcass proper is constructed from bead wires and a cylinder of uncured rubbers which is shaped to make it toroidal; then, on what is called a xe2x80x9csecond-stagexe2x80x9d machine, or alternatively a xe2x80x9cfinishingxe2x80x9d machine, on which a cylindrical crown reinforcement, or belt, and a tread are applied to this carcass; finally, the entire unit is vulcanised in a mold.
In this method of manufacture, between the two main stages described above, it is necessary to store or possibly transport the uncured carcass from the building machine to the finishing machine, in a state in which it is highly deformable, since the rubber is in the plastic, non-vulcanised, state. Formerly, the carcasses were attached to brackets, the axes of the carcasses being horizontal, but, under the effect of their own weight they became deformed into an oval; then the carcasses were laid flat, their axes being vertical. However, with the increase in the weight of tires, it was noted that the upper sidewall sags.
Devices were therefore conceived to avoid this deformation. Thus U.S. Pat. No. 4,452,655 describes a support means for an uncured tire carcass comprising two beads, with its axis vertical. This elliptical support means comprises four vertical plates capable of accepting a certain elastic flexion which enables them to engage beneath the upper bead in order to hold the carcass, the plates being distributed over the two minor arcs of the ellipse.
The carcass is thus held on the support by the plates bearing against said carcass beneath the upper bead, the carcass opposing radial extension of the plates. The thrust forces exerted on the carcass, which are irregularly distributed over the circumference of the carcass owing to the elliptical shape of the support means, risk causing deformation of the carcass.
Furthermore, the support means, in order to be able to accept carcasses of different dimensions, utilizes the flexibility of the plates, which indicates that carcasses of smaller dimensions are subject to greater stresses and hence greater risks of deformation. In order to avoid this phenomenon, each tire dimension requires a corresponding size of the device, which is therefore no longer multidimensional.
Finally, the operation of unloading the carcass is complicated, and cannot be automated. In fact, it is necessary to displace the carcass transversely and tilt it in order to disengage one of its sides, then to bring it back in the opposite direction in order to disengage the other side and thus free the whole carcass.
Note that xe2x80x9ccarcassxe2x80x9d designates the raw blank that results from the operations performed in the first stage.
The present invention is directed at overcoming all these disadvantages.
In order to do this, the invention proposes a device for the substantially vertical suspension of tire carcasses, comprising a plurality of supports distributed about a lifting axis XXxe2x80x2, which are mounted on a handling plate and are able to bear on the inside of a tire carcass, the supports being mobile radially relative to the suspension axis between at least one retracted loading/unloading position for the carcass and at least one spread-apart holding position for the carcass, said device comprising a system having at least one spring which exerts a radial expansion force on the supports, this expansion being able to be limited by a stop which limits the radial stroke of the supports.
Such a device makes it possible to limit the radial force exerted on the carcasses. This makes it possible to optimize the uniformity of the tire. The steps of loading and unloading the carcass are particularly easy to perform, and lend themselves well to automation.
The limitation of the expansion of the arms and the form of the supports enable the carcass to be put in place and, more precisely, the upper bead of the carcass, the latter being submitted with its axis vertical, to be allowed to pass over the supports in order to position it without the bead being subjected to the stress exerted by the spring during this displacement. Since the putting in place of the carcass then disengages the stop, the supports can come to bear on the carcass beneath the upper bead.
Advantageously, the stop is arranged on an actuating lever. This actuating lever is capable of being actuated, in order to disengage said stop, by the putting the carcass to be suspended on the device.
This arrangement with the lever greatly facilitates putting the carcass in place since the passage of the supports into the spread-apart position for holding the carcass is controlled automatically by simply putting the carcass in place.
The radial stroke of the supports permitted by said stop is preferably adjustable, the adjustment of the stroke being effected by modifying the distance of the stop relative to the lifting axis XXxe2x80x2.
This characteristic makes it possible to suspend carcasses of different dimensions on the same device. The operator merely has to adjust the distance of spreading of the supports according to the diameter of the carcass to be suspended.
Furthermore, the tension of the spring is advantageously adjustable.
Thus, the force to which the carcass is subjected is adjusted, according to the type of product being manufactured and its dimensions, so as to ensure the integrity of the carcass. It is thus possible to provide for the expansion force which is exerted on the supports to be substantially the same whatever the dimension of the carcass to be suspended.
Advantageously, the supports are distributed regularly relative to the vertical axis and comprise respectively a bearing surface intended to be in contact with the carcass to be suspended, the envelope of these bearing surfaces forming a substantially cylindrical surface. Thus the forces exerted by the supports on the carcass to be suspended are distributed substantially uniformly over the circumference of the latter.
According to an advantageous variant, the radial displacements of the supports are controlled by at least one connecting-rod articulated on one hand to the supports and, on the other hand, to a ring which slides along the axis of suspension XXxe2x80x2. It is then possible to provide a piston-cylinder unit which makes it possible to bring the supports towards the suspension axis XXxe2x80x2 by displacing the ring.
Such a variant lends itself particularly well to automation.
According to another aspect of the present invention, there is provided a device for the substantially vertical suspension of tire carcasses, comprising an assembly provided with at least two supports which are distributed about a lifting axis X-Xxe2x80x2, which are mounted on a handling plate and are able to bear on the inside of a tire carcass, the supports being mobile radially relative to the lifting axis between at least one retracted loading/unloading position for the carcass and at least one spread-apart holding position for the carcass, each of the supports being associated with a sliding rack arm which cooperates with a toothed wheel borne by the handling plate, said wheel coordinating the translational movements of said arms so as to move them apart from or towards the lifting axis XXxe2x80x2 simultaneously.
Such an arrangement makes it possible to use, for example, a single spring which can act on two, four or even more supports. Although it is advantageous to arrange the supports in pairs, it is also possible to use an uneven number of supports. These are then preferably distributed uniformly around the suspension axis.
According to another aspect, the invention also provides for a process for building a tire, comprising the steps:
performing a first stage of producing a carcass;
arranging said carcass on a suspension device having mobile supports on which said supports have been positioned beforehand in the retracted position;
positioning said supports in the spread-apart position, against the inner walls of the carcass;
disengaging said carcass from said suspension device by positioning said supports of the device in the retracted position;
carrying out a second stage of arranging on said carcass at least the finishing elements in order to produce a tire;
vulcanising the tire thus produced.
This process is particularly advantageous since it makes it possible to optimize the uniformity of the tire. The radial mobility of the supports makes it possible to place and remove the carcass very simply, inexpensively and ergonomically. The simultaneous bringing together of the arms in fact makes it possible to achieve a retracted position of the arms in which the latter are no longer in contact with the carcass, which permits easy and simple loading and/or unloading of said carcass.
This process furthermore lends itself well to automation.
In order for the suspension device to be multidimensional, the radial distance of the stop of the lever from the vertical axis is adjustable according to the dimension of the carcass to be suspended.
Other characteristics and advantages of the invention will become apparent on reading the examples of embodiments of the suspension device for tire carcasses according to the invention, which are given in non-limitative manner.